Organic electroluminescence device

ABSTRACT

An organic electroluminescence device which comprises laminating layers in the order of anode/light emitting layer/adhesive layer/cathode, or anode/hole-injecting layer/light emitting layer/adhesive layer/cathode, the energy gap of the light emitting layer being larger than that of 8-hydroxyquinoline or metal complex thereof and contained in the adhesive layer, the light emitting layer comprising a compound which emits a blue, greenish blue or bluish green light in CIE chromaticity coordinates, and the adhesive layer including a metal complex of 8-hydroxyquinoline or a derivative thereof and at least one organic compound in an arbitrary region in the direction of the thickness of the layer, the thickness of which is smaller than that of the above-mentioned light emitting layer. 
     According to the above organic electroluminescence device, improvements in uniformity in light emission and emission efficiency are realized.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescence device,and more particularly, to an organic electroluminescence device capableof improving the uniformity of light emission and retarding the loweringin initial luminances.

2. Description of the Relates Arts

Since an electroluminescence device (hereinafter referred to as ELdevice) has features in a high self-distinguishability because of itsself-emission, and having a high impact resistance because it is acompletely solid device, various devices using inorganic and organiccompounds are proposed at present and attempts to put them into practiceuse have been made. Among these devices, organic EL devices permitdrastically low voltage to be applied, and therefore developments ofvarious materials for these devices as well as devices have beenundertaken.

The above organic EL device basically comprises anode/light emittinglayer/cathode, and those which are provided with a hole injecting layeror electron-injecting layer at need for improving the light emittingproperty. In this structure of the device, the cathode must besufficiently adhered to the light emitting layer. If the adhesivity isnot sufficient, the mechanical strength of the device becomes low,causing ununiform light emission, and in the worst case non-emissionregions. Furthermore, ununiformity of the load in the light emittingface is caused, which accelerates the deterioration to shorten thelifetime of the device, and this is an obstacle to practical use of thedevice.

Heretofore, it has been known that an electron-injecting layer or a holebarrierer layer is provided, at need, between the light emitting layerand the cathode. In these techniques, particularly when the latter layeris provided, the material is selected depending on the difference fromthe light emitting layer in the energy level, and the material must fitto this concept. An example of them is a technique of "providing a holeblocking layer (hole barrier layer) having a first oxidation voltage 0.1V higher than that of the light emitting layer, between the lightemitting layer and the cathode" (Japanese Patent Application Laid-OpenNo. 195683/1990). Also in Japanese Patent Application Nos. 195683/1990and 255788/1990, 8-hydroxyquinoline derivative is used as the holebarrier layer basing on the above concept, but the emission efficiencyof blue lights in these arts are still so low as 0.3 (1 m.W⁻¹). On theother hand, when the materials described in Japanese Patent ApplicationLaid-Open No. 231070/1991 and Japanese Patent Application No.279304/1990 are used for the light emitting layer, an emission of bluelight in a high brightness can be obtained. These materials arementioned as effective materials for full-colorization of flat paneldisplays and the like in future. However, when these materials areformed to devices in the structure of anode/light emittinglayer/cathode/, or anode/hole injecting layer/light emittinglayer/cathode as described before, ununiform emission or non-emissionregion are sometimes caused, which have brought about problems inanalyzing the practical use of the devices concerning lifetime of thedevice, minute processing of the device.

On the other hand, as the means to dissolve the above-mentionedproblems, the doping technique (Japanese Patent Application Laid-OpenNo. 255190/1991, The Institute of Electronics, Information andCommunication Engineers(IEICE) Technical Report (vol. 91, No. 406(1991),p47), Polymer Preprints Japan (vol. 40, No. 10 (1991))) and the likehave been disclosed.

These aim at improving the properties by contaminating a secondcomponent into the light emitting layer. However, when the secondcomponent is contaminated into the light emitting layer, a possible fallin emission efficiency or change in the color of the emitting light havehad to be considered sufficiently.

SUMMARY OF THE INVENTION

Under these circumstances, after intensively studying the adhesivitybetween the light emitting layer and the cathode, the present inventorsfound that an EL device having an improved uniformity of light emissionand an improved emission efficiency can be obtained by contaminating asecond component into the layer (adhesive layer) to improve theadhesivity between the light emitting layer and the cathode, withoutchanging the color of the emission light, while the characteristics ofEL devices maintained.

The present invention has been accomplished on the basis of such aknowledge.

That is, the present invention provides an organic electroluminescencedevice which comprises laminating layers in the order of anode/lightemitting layer/adhesive layer/cathode, or anode/hole injectinglayer/light emitting layer/adhesive layer/cathode, the energy gap of thelight emitting layer being larger than that of 8-hydroxyquinoline ormetal complex thereof and contained in the adhesive layer, and theadhesive layer including a metal complex of 8-hydroxyquinoline or aderivative thereof and at least one organic compound in an arbitraryregion in the direction of the thickness of the layer, the thickness ofwhich is smaller than that of the above-mentioned light emitting layer.

The present invention also provides an organic electroluminescencedevice which comprises laminating layers in the order of anode/lightemitting layer/adhesive layer/cathode, or anode/hole-injectinglayer/light emitting layer/adhesive layer/cathode, the light emittinglayer comprising a compound which emits a blue, greenish blue or bluishgreen light in CIE chromaticity coordinates, the adhesive layerincluding a metal complex of 8-hydroxyquinoline or a derivative thereofand at least one organic compound in an arbitrary region in thedirection of the thickness of the layer, the thickness of which issmaller than that of the above-mentioned light emitting layer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The organic EL device of the present invention comprises laminatinglayers in the order of anode/light emitting layer/adhesivelayer/cathode, or anode/hole injecting layer/light emittinglayer/adhesive layer/cathode.

As to the anode in the organic EL device of the present invention, ametal, an alloy, an electro-conducting compound or a mixture thereof,all having a large work function (not less than 4 eV), is preferablyused as an electrode material. Specific examples of these electrodematerials are metals such as Au, and a dielectric transparent materialssuch as Cul, ITO, SnO₂, and ZnO. Said anode can be prepared by formingsaid electrode material into thin film by vapor deposition orsputtering. To obtain light emission from said electrode, it ispreferable that the transmittance of the electrode is more than 10% andthe resistance of the sheet as an electrode is not more than severalhundred Ω/□.

The film thickness of the anode is usually in the range of 10 nm to 1μm, preferably 10 to 200 nm, depending upon the material.

On the other hand, as the cathode, a metal, an alloy, anelectroconducting compound or a mixture thereof, all having a small workfunction (not more than 4 eV) is preferably used as an electrodematerial. Specific examples of such electrode materials are sodium, asodium-potassium alloy, magnesium, lithium, a mixture of magnesium andcopper, Al/AlO₂, indium, and rare earth metals. Said cathode can beprepared by forming said electrode material into thin film by vapordeposition or sputtering. The resistance of the sheet as an electrode ispreferably not more than several hundred Ω/□. The film thickness isusually in the range of 10 nm to 1 μm, preferably 50 to 200 nm. In theEL device of the present invention, it is preferable that either anodeor cathode be transparent or translucent because light emission istransmitted and obtained with a high efficiency.

Next, the light emitting layer in the above-mentioned device possesses,similarly to the conventional light emitting layer, (i) injectingfunction (at application of voltage, holes can be injected from theanode or the hole-injecting layer, and electrons can be injected fromthe cathode or the electron-injecting layer), (ii) transporting function(positive holes and electrons can be moved by the power of electricfield), and (iii) light emitting function (to provide a place forrecombination of holes and electrons, permitting light emission). Thethickness of said layer is not particularly limited, but can beappropriately selected depending on circumstances, and it is preferably1 nm to 10 μm, and particularly preferably 5 nm to 5 μm.

The light emitting layer of the present invention is characterized byhaving an energy gap larger than that of 8-hydroxyquinoline or metalcomplex thereof contained in the adhesive layer, and comprising acompound which emits blue, greenish blue, or bluish green light in CIEchromaticity coordinates.

Therein, energy gap means a value of energy corresponding to thewavelength of absorption ends of the absorption spectrum of thin film,indicating the value corresponding to the difference in energy betweenthe maximum population level and the minimum population level ofelectron orbit. Said value of energy gap can be determined from theabsorption ends of the absorption spectrum of thin film to be used, orthe measurement by internal photoelectric effect using a material ofknown work function as the electrode.

Specific examples of the material of this light emitting layer aretetraphenylbutadiene compounds (see Japanese Patent Application No.96990/1992) and compounds represented by general formula (I), (II) and(III) as follows. ##STR1## wherein R¹ to R⁴ indicate each a hydrogenatom, an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having1 to 6 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, asubstituted or unsubstituted aryl group having 6 to 18 carbon atoms, asubstituted or unsubstituted cyclohexyl group, a substituted orunsubstituted aryloxyl group having 6 to 18 carbon atoms, or an alkoxylgroup having 1 to 6 carbon atoms; therein, the substituent is an alkylgroup having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbonatoms, an aralkyl group having 7 to 8 carbon atoms, an aryloxyl grouphaving 6 to 18 carbon atoms, an aryl group having 1 to 6 carbon atoms,an acyloxyl group having 1 to 6 carbon atoms, a carboxyl group, a styrylgroup, an arylcarbonyl group having 6 to 20 carbon atoms, anaryloxycarbonyl group having 6 to 20 carbon atoms, an alkoxycarbonylgroup having 1 to 6 carbon atoms, a vinyl group, an anilinocarbonylgroup, a carbamoyl group, a phenyl group, a nitro group, a hydroxylgroup or a halogen; these substituents may be used solely or in plural;R¹ to R⁴ may be identical to or different from one another, and R¹ andR² and R³ and R⁴ may combine with groups substituting each other to forma substituted or unsubstituted saturated five-membered ring or asubstituted or unsubstituted saturated six-membered ring; Ar indicates asubstituted or unsubstituted arylene group having 6 to 20 carbon atoms,a single bond, or a conjugated polyene 2 to 6 carbon atoms; an arylenegroup therein may be mono-substituted or poly-substituted, and itsposition may be any of ortho-, para- and meta-; however, when Ar is anunsubstituted phenylene, R¹ to R⁴ is each selected from the groupconsisting of an alkoxyl group having 1 to 6 carbon atoms, an aralkylgroup having 7 to 8 carbon atoms, a substituted or unsubstitutednaphthyl group, a biphenyl group, a cyclohexyl group, and an aryloxylgroup, general formula (II):

    A--Q--B                                                    (II)

wherein A and B indicate each a monovalent group which is obtained byremoving a hydrogen atom from the compound represented by the abovegeneral formula (I), and may be identical to or different from eachother; Q indicates a divalent group breaking the conjugation, or generalformula (III) ##STR2## wherein A¹ indicates a substituted orunsubstituted arylene group having 6 to 20 carbon atoms or a divalentaromatic heterocyclic group; its position may be any of ortho-, meta-and para-; A² is a substituted or unsubstituted aryl group having 6 to20 carbon atoms or a monovalent aromatic heterocyclic group; R⁵ and R⁶indicate each a hydrogen atom, a substituted or unsubstituted aryl grouphaving 6 to 20 carbon atoms, a cyclohexyl group, a monovalent aromaticheterocyclic group, an alkyl group having 1 to 10 carbon atoms, anaralkyl group having 7 to 20 carbon atoms or an alkoxyl group having 1to 10 carbon atoms; R⁵ and R⁶ may be identical to or different from eachother; the mono-substituent therein is an alkyl group, an aryloxylgroup, an amino group or a phenyl group with or without a substituent;each substituent of R⁵ may combine with A¹ to form a saturated orunsaturated five-membered ring or six-membered ring, and similarly eachsubstituent of R⁶ may combine with A² to form a saturated or unsaturatedfive-membered ring or six-membered ring; Q indicates a divalent groupbreaking a conjugation, and emits a blue, greenish blue or bluish greenlight in CIE chromaticity coordinates, said adhesive layer being a layerincluding a metal complex of 8-hydroxyquinoline or its derivative and atleast one of organic compound in an arbitrary region in the direction ofthe thickness of the layer, the thickness of which is smaller than thatof the above-mentioned light emitting layer.

Herein, R¹ to R⁴ in general formula (I) may be identical to or differentfrom one another as described before, and each indicates a hydrogenatom, an alkyl group having 1 to 6 carbon atoms (such as a methyl group,an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, ani-butyl group, a sec-butyl group, a tert-butyl group, an isopentylgroup, a t-pentyl group, a neopentyl group, and an isohexyl group), analkoxyl group having 1 to 6 carbon atoms (such as a methoxyl group, anethoxyl group, a propoxyl group, and a butoxyl group), an aralkyl grouphaving 7 to 8 carbon atoms (such as a benzyl group, and a phenethylgroup), an aryl group having 6 to 18 carbon atoms (such as a phenylgroup, a biphenyl group, and a naphthyl group), a cyclohexyl group, oran aryloxyl group having 6 to 18 carbon atoms (such as a phenoxyl group,a biphenyloxyl group, and a naphthyloxyl group).

R¹ to R⁴ may be groups resulted by combining the above withsubstituents. Specifically, R¹ to R⁴ indicate each asubstituent-containing phenyl group, a substituent-containing aralkylgroup, a substituent-containing cyclohexyl group, asubstituent-containing biphenyl group, or a substituent-containingnaphthyl group. The substituent therein includes an alkyl group having 1to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, anaralkyl group having 7 to 8 carbon atoms, an aryloxyl group having 6 to18 carbon atoms, an acyl group having 1 to 6 carbon atoms, an acyloxylgroup having 1 to 6 carbon atoms, an aryloxycarbonyl group having 6 to20 carbon atoms, a carboxyl group, a styryl group, an arylcarbonyl grouphaving 6 to 20 carbon atoms, an alkoxycarbonyl group having 1 to 6carbon atoms, a vinyl group, an anilinocarbonyl group, a carbamoylgroup, a phenyl group, a nitro group, a hydroxyl group or a halogen, andmay be poly-substituted. Accordingly, for example, asubstituent-containing aralkyl group includes alkyl group-substitutedaralkyl groups (such as methylbenzyl group, and methylphenethyl group),alkoxyl group-substituted aralkyl groups (such as methoxybenzyl groupand an ethoxyphenethyl group), aryloxyl group-substituted aralkyl groups(such as phenoxybenzyl group, and naphthyloxyphenethyl group), phenylgroup-substituted aralkyl group (such as phenylphenethyl group);above-mentioned substituent-containing phenyl groups include alkylgroup-substituted phenyl groups (such as tolyl group, dimethylphenylgroup, and ethylphenyl group), alkoxyl group-substituted phenyl groups(such as methoxyphenyl group, and ethoxyphenyl group), aryloxylgroup-substituted phenyl groups (such as phenoxyphenyl group, andnaphtyloxyphenyl group) and phenyl group-substituted phenyl group (thatis, biphenylyl group). Substituent-containing cyclohexyl groups includealkyl group-substituted cyclohexyl group (such as methylcyclohexylgroup, dimethylcyclohexyl group, and ethylcyclohexyl group), alkoxygroup-subsituted cyclohexyl groups (such as methoxycyclohexyl group, andethoxycyclohexyl group), aryloxyl group-substituted cyclohexyl groups(such as phenoxycyclohexyl group, and naphthyloxycyclohexyl group), andphenyl group-substituted cyclohexyl groups (such as phenylcyclohexylgroup). Substituent-containing naphthyl groups include alkylgroup-substituted naphthyl groups (such as methylnaphtyl group, anddimethylnaphthyl group), alkoxyl group-substituted naphthyl group (suchas methoxynaphthyl group, and ethoxynaphthyl group), aryloxylgroup-substituted naphthyl group (such as phenoxynaphthyl group andnaphthyl oxylnaphthyl group), and phenyl group-substituted naphthylgroup.

As R¹ to R⁴, among the above, each an alkyl group having 1 to 6 carbonatoms, an aryloxyl group, a phenyl group, a naphthyl group, a biphenylgroup, or a cyclohexyl group is preferable. They may be substituted orunsubstituted. R¹ to R⁴ may be identical to or different from oneanother, and R1 and R² and R³ and R⁴ may combine with the substituentsone another to form a substituted or unsubstituted saturatedfive-membered ring or substituted or unsubstituted saturatedsix-membered ring.

On the other hand, Ar in general formula (I) indicates a substituted orunsubstituted aryl group having 6 to 20 carbon atoms, that is, anarylene group such as a substituted or unsubstituted phenylene group, abiphenylene group, p-terphenylene group, a naphthylene group, aterphenylene group, a naphthalenediyl group, an anthracenediyl group,phenanthrenediyl group, and a phenalenediyl group, and may beunsubstituted or substituted. The position of methylidine (═C═CH--) maybe any of ortho-, meta-, and para-. However, when Ar is an unsubstitutedphenylene, R¹ to R⁴ are each selected from the group consisting of analkoxyl group having 1 to 6 carbon atoms, an aralkyl group having 7 to 8carbon atoms, a substituted or unsubstituted naphthyl group, a biphenylgroup, a cyclohexyl group, and an aryloxyl group. The substituentincludes an alkyl group (such as a methyl group, an ethyl group, an-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, asec-butyl group, a t-butyl group, an isopentyl group, a t-pentyl group,a neopentyl group, and an isohexyl group), an alkoxyl group (such as amethoxyl group, an ethoxyl group, a propoxyl group, an i-propoxyl group,a butyloxyl group, an i-butyloxyl group, a sec-butyloxyl group, at-butyloxyl group, an isopentyloxyl group, and a t-pentyloxyl group), anaryloxyl group (such as a phenoxyl group, and a naphthyloxyl group), anacyl group (such as a formyl group, an acetyl group, a propionyl group,and a butylyl group), an acyloxyl group, an aralkyl group (such as abenzyl group, and a phenethyl group), a phenyl group, a hydroxyl group,a carboxyl group, an anilinocarbonyl group, a carbamoyl group, anaryloxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group,a butoxycarbonyl group, a nitro group, and a halogen, and may bemono-substituted or poly-substituted.

Dimethylidine aromatic compound represented by the above-mentionedformula (I) contains two methylidine units (═C═CH--) in one molecule,varying in four combinations according to the geometrical isomerism ofsaid methylidine unit, that is, cis-cis, trans-cis, cis-trans andtrans-trans. The light emitting layer of the present invention may beany of them, or may be mixtures of geometrical isomers. Particularlypreferred one comprises trans isomer only.

The above-mentioned substituent may combine among substituents to form asubstituted or unsubstituted saturated five-membered ring orsix-membered ring.

A and B in general formula (II) indicate each a monovalent groupresulted by removing one hydrogen atom from the compounds represented bythe above-mentioned general formula (I), and may be identical to ordifferent from each other. Therein Q indicates a divalent group breakingthe conjugation.

The conjugation therein is attributed to the delocalization ofπ-electron, and includes a conjugated double bond or a conjugation dueto an unpaired electron or a lone electron-pair. Q indicatesspecifically a divalent group which results from removing each onehydrogen atom from a straight chain alkane, such as: ##STR3##

The divalent group breaking the conjugation is thus used for the purposethat EL emission light obtained when A or B shown in above (that is, thecompound of general formula (I)) is used solely as the organic EL deviceof the present invention and the EL emission light obtained when thecompound represented by general formula (II) is used as the organic ELdevice of the present invention may be identical in color. In otherwords, said divalent group is used so that the wavelength of the lightemitting layer represented by general formula (I) or general formula(II) may not be changed to shortened or lengthened. By combining with adivalent group to break conjugation, it is confirmed that the glasstransition temperature (Tg) rises, and uniform pinhole free minutecrystal or amorphous thin film can be obtained, improving the uniformityof light emission. Further, combining with a divalent group breaking theconjugation brings about advantages that EL emission is notlong-wavened, and synthesis or purification can be easily effected.

Moreover, A¹ in general formula (III) indicates an arylene group having6 to 20 carbon atoms, and a divalent aromatic heterocyclic group, and A²indicates an aryl group having 6 to 20 carbon atoms (such as a phenylgroup, a biphenyl group, and a naphthyl group), or a monovalent aromaticheterocyclic group. R⁵ and R⁶ indicates each a hydrogen atom, asubstituted or unsubstituted aryl group having 6 to 20 carbon atoms, acyclohexyl group, a monovalent aromatic heterocyclic group, an alkylgroup having 1 to 10 carbon atoms (such as a methyl group, an ethylgroup, a n-propyl group, an i-propyl group, a n-butyl group, an i-butylgroup, a sec-butyl group, a tert-butyl group, an isopentyl group,at-pentyl group, a neopentyl group, and an isohexyl group), an aralkylgroup having 7 to 20 carbon atoms (such as a benzyl group, and aphenethyl group), or an alkoxyl group having 1 to 10 carbon atoms (suchas a methoxyl group, an ethoxyl group, a propoxyl group, and a buthoxylgroup). R⁵ and R⁶ may be identical to or different from each other. Asubstituent therein is, in mono-substitution, an alkyl group, anaryloxyl group, an amino group or a substituted or unsubstituted phenylgroup. Each substituent in R⁵ may combine with A¹ to form a saturated orunsaturated five-membered ring or six-membered ring, and similarly eachsubstituent in R⁶ may combine with A² to form a saturated or unsaturatedfive-membered ring or six-membered ring. Q indicates a divalent groupbreaking conjugation as described above.

Further, in the present invention, the light emitting layer representedby general formula (I), general formula (II) or general formula (III)must be a compound providing an emission of blue, greenish blue orbluish green light in CIE chromaticity coordinates.

The above-mentioned light emitting layer can be prepared by forming theabove compound into thin film by a known method such as the vapordeposition method, the spin-coating method, the casting method or the LBmethod, but particularly, a molecular accumulated film is preferable. Amolecular accumulated film therein is a thin film formed by depositingsaid compound from a gaseous state, or a thin film formed bysolidification of said compound from a solution or liquid state.Usually, said molecular accumulated film is distinguished from a thinfilm (molecular built-up film) formed by the LB method, by thedifference in the aggregation structure or the higher-order structure,or the functional difference resulting therefrom.

Said light emitting layer, as disclosed in Japanese Patent ApplicationLaid-Open No. 194393/1984, can be formed by dissolving a binding agentsuch as a resin and said compound in a solvent to prepare solution,which is formed into thin film by the spin-coating method and the like.

The film thickness of the light emitting layer thus formed is notparticularly limited, and can be determined appropriately according tothe circumstances. Usually, it is preferably in the range of 1 nm to 10μm, particularly preferably 5 nm to 5 μm.

As described above, the light emiting layer of the present invention hasan injection function of injecting holes from the anode or thehole-injecting layer, and electrons from the cathode or the adhesive andtransporting layer upon application of an electric field, a transportfunction of transporting injected charges (holes and electrons) by theaction of an electric field, and a light emitting function of providinga field for recombination of electrons and holes, thereby emittinglight. There may be a difference in between injectability of holes andelectrons, and a difference in transporting ability represented bymobilities of holes and electrons, but it is preferable to move eitherone.

Herein examples of compounds to be used as the above-mentioned lightemitting layer are shown as follows. ##STR4##

Next, the hole injecting layer in the present invention is notnecessarily required for the present device, but is preferably used forthe purpose of improving the emission ability. The preferable materialof said hole-injecting layer is one which transports holes to the lightemitting layer at a lower electric field, and still more preferably thetransportation of holes is made at least 10⁻⁶ cm² /volt.sec in anelectric field of 10⁴ to 10⁶ volt/cm. For example, arbitrary materialcan be selected and used from the conventionally used ones as theelectric charges injecting and transporting material for holes and theknown ones to be used for the hole-injecting layer of EL devices inconventional photo-conducting materials.

Examples of materials for hole-injecting layer are triazole derivatives(described in the specification of U.S. Pat. No. 3,112,197, etc.),oxadiazole derivatives (described in the specification of U.S. Pat. No.3,189,447, etc.), imidazole derivatives (described in Japanese PatentPublication No. 16096/1962, etc.), polyarylalkane derivatives (describedin the specifications of U.S. Pat. Nos. 3,615,402, 3,820,989 and3,542,544, and in Japanese Patent Publication Nos. 555/1970 and10983/1976, and further in Japanese Patent Application Laid-Open Nos.93224/1976, 17105/1980, 4148/1981, 108667/1980, 156953/1980 and36656/1981, etc.), pyrazoline derivatives or pyrazolone derivatives(described in the specifications of U.S. Pat. Nos. 3,180,729 and4,278,746, and in Japanese Patent Application Laid-Open Nos. 88064/1980,88065/1980, 105537/1974, 51086/1980, 80051/1981, 88141/1981, 45545/1982,112637/1979 and 74546/1970, etc.), phenylenediamine derivatives(described in the specification of U.S. Pat. No. 3,615,404, and inJapanese Patent Publication Nos. 10105/1976, 3712/1971 and 25336/1972,and further in Japanese Patent Application Laid-Open Nos. 53435/1979,110536/1979 and 119925/1979, etc.), arylamine derivatives (described inthe specification of U.S. Pat. Nos. 3,567,450, 3,180,703, 3,240,597,3,658,520, 4,232,103, 4,175,961 and 4,012,376, and in Japanese PatentPublication Nos. 35702/1974 and 27577/1964, and further in JapanesePatent Application Laid-Open Nos. 144250/1980, 119132/1981 and22437/1981, and German Patent No. 1,110,518, etc.), amino-substitutedchalcone derivatives (described in the specification of U.S. Pat. No.3,526,501, etc.), oxazole derivatives (described in the specification ofU.S. Pat. No. 3,257,203, etc.), styrylanthracene derivatives (describedin Japanese Patent Application Laid-Open No. 46234/1981, etc.),fluorenone derivatives (described in Japanese Patent ApplicationLaid-Open No. 110837/1979, etc.), hydrazone derivatives (described inthe specification of U.S. Pat. No. 3,717,462, and in Japanese PatentApplication Laid-Open Nos. 59143/1979, 52063/1980, 52064/1980,46760/1980, 85495/1980, 11350/1982, 148749/1982, and 311591/1990, etc.),and stilbene derivatives (described in Japanese Patent ApplicationLaid-Open Nos. 210363/1986, 228451/1986, 14642/1986, 72255/1986,47646/1987, 36674/1987, 10652/1987, 30255/1987, 93445/1985, 94462/1985,174749/1985, and 175052/1985, etc.)

Further, examples of hole-injecting and transporting materials aresilazane derivatives (described in the specification of U.S. Pat. No.4,950,950), polysilane based material (described in Japanese PatentApplication Laid-Open No. 204996/1990), aniline-based copolymer(described in Japanese Patent Application Laid-Open No. 282263/1990),and electrically conductive high molecular oligomer disclosed in thespecification of Japanese Patent Application No. 211399/1989, amongthem, thiophene oligomer.

In the present invention, the above compounds can be used as ahole-injecting compound, but it is preferred to use porphyrin compounds(described in Japanese Patent Application Laid-Open No. 2956965/1988,etc.), aromatic tertiary amine compounds or styrylamine compounds(described in the specification of U.S. Pat. No. 4,127,412, and JapanesePatent Application Laid-Open Nos. 27033/1978, 58445/1979, 149634/1979,64299/1979, 79450/1980, 144250/1980, 119132/1981, 295558/1986,98353/1986 and 295695/1988), and most preferably, said aromatic tertiaryamine compounds are used.

Representative examples of said porphyrin compounds are porphin;1,10,15,20-tetraphenyl-21H,23H-porphin copper (II),1,10,15,20-tetraphenyl-21H,23H-porphin zinc (II),5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphin, siliconphthalocyanine oxide, aluminum phthalocyanine chloride,phthalocyanine (nonmetal), dilithium phthalocyanine, coppertetramethylphthalocyanine, copper phthalocyanine, chrome phthalocyanine,zinc phthalocyanine, lead phthalocyanine, titanium phthalocyanine oxide,magnesium phthalocyanine, and copper octamethylphthalocyanine.

Representative examples of said aromatic tertiary amine compounds orstyrylamine compounds are N,N,N',N'-tetraphenyl-4,4'-diaminophenyl,N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diaminobiphenyl (TPDA),2,2-bis(4-di-p-tolylaminophenyl)propane,1,1-bis(4-di-p-tolylaminophenyl)-cyclohexane,N,N,N',N'-tetra-p-tolyl-4,4'-diaminobiphenyl,1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane,bis(4-dimethylamino-2-methylphenyl)phenylmethane,bis(4-di-p-tolylaminophenyl)phenylmethane,N,N'-diphenyl-N,N'-di(4-methoxyphenyl)-4,4'-diaminobiphenyl,N,N,N',N'-tetraphenyl-4,4'-diaminodiphenylether,4,4'-bis(diphenylamino)quadriphenyl, N,N,N-tri(p-tolyl)amine,4-(di-p-tolylamino)-4'-[4(di-p-tolylamino)styryl]stilbene,4-N,N-diphenylamino-(2-diphenylvinyl)benzene,3-methoxy-4'-N,N-diphenylaminostilbene, N-phenylcarbazole, and aromaticdimethylidine-based compounds.

The hole injecting layer in the EL device of the present invention canbe obtained by forming the above compound into a film by the knownmethod of film forming such as the vacuum deposition method, the spincoating method, the casting method, and the LB method. The filmthickness as said hole injecting layer is not particularly limited, butusually 5 nm to 5 μm.

The hole injecting layer may consist of one layer comprising one or twoor more of these hole-injecting and transporting materials, or may be alaminate of hole injecting layer comprising other compounds than thebefore-mentioned hole injecting layer.

As the structure of the organic EL device to be obtained according tothe present invention, the layer (adhesive layer) newly added to improvethe adhesivity betweeen the light emitting layer and the cathode isdesired to contain a material having a high adhesivity to the lightemitting layer and the cathode. As the material having such anadhesivity, metal complexes of 8-hydroxyquinoline or derivative thereofare mentioned. Specific example of them are metal chelated oxinoidecompound containing chelates of oxine (generally, 8-quinolinol or8-hydroxyquinoline). These compounds exhibits high level properties, andare easy to be formed into thin film. Examples of the oxinoide compoundssatisfy the structural formula as under. ##STR5## wherein Mt indicates ametal, n is an integer of 1 to 3, and Z indicates an atom required tocomplete at least two condensed aromatic ring, being locatedindependently.

Therein metals represented by Mt are those which can be monovalent,divalent or trivalent metals, that is, alkali metals such as lithium,sodium and potassium, alkaline earth metals such as magnesium andcalcium, and earth metals such as boron and aluminum.

Generally any of monovalent, divalent and trivalent metals which areknown to be useful chelated compounds can be used therein.

Z indicates an atom to form a hetero ring comprising azole or azine asone of at least two condensed aromatic rings. Herein, if necessary,another ring can be added to the above-mentioned condensed aromaticring. Moreover, in order to avoid adding bulky molecules withoutimprovement in function, the number of the atoms shown by Z ispreferably kept to not more than 18.

Further, specific examples of the chelated oxinoide compounds aretris(8-quinolinol)aluminum, bis(8-quinolinol)magnesium,bis(benzo-8-quinolinol)zinc, bis(2-methyl-8-quinolato)aluminumoxide,tris(8-quinolinol)indium, tris(5-methyl-8-quinolinol)aluminum,8-quinolinol lithium, tris(5-chloro-8-quinolinol)gallium,bis(5-chloro-8-quinolinol)calcium,tris(5,7-dichloro-8-quinolinol)aluminum,tris(5,7-dibromo-8-hydroxyquinolinol)aluminum,bis(8-quinolinol)beryllium, bis(2-methyl-8-quinolinol)beryllium,bis(8-quinolinol)zinc, bis(2-methyl-8-quinolinol)zinc,bis(8-quinolinol)tin, and tris(7-propyl-8-quinolinol)aluminum.

The adhesive layer in the present invention comprises preferably, inaddition to the above compound, further one or more compounds. Said oneor more compounds are sufficient if they are soluble in the samesolvents of metal complexes of 8-hydroxyquinoline or derivative thereof,or depositable without being decomposed under appropriate conditions.Such compounds are sufficient if contaminated in an arbitrary region inthe direction of the thickness of the adhesive layer. If thecontamination of these additional compounds are 0.01 mol % or more, thefilm is kept from crystallization, allowing a constant driving of thedevice.

Further, it is desired that the metal complex of 8-hydroquinoline or itsderivative is the largest in the ratio of molecule number in theadhesive layer. It is to maintain a stable adhesivity with metalelectrode contaminated with any compound. Therein, if the metal complexof 8-hydroquinoline or its derivative is smaller than other compounds inthe ratio of molecule number in the adhesive layer, the adhesive layeris easy to be removed from the metal electrode.

It is further preferred that the device is adjusted so that the voltagerequired to emit the initial luminaries after 100 hours of continuousdriving is not more than 1.1 times the initial voltage. Since thevoltage during the initial continuous 100 hours of driving usuallyfluctuates widely, keeping the fluctuation in the voltage constant canreduce the burden on the driving system.

Specific examples of the compounds contained in the adhesive layer inaddition to metal complexes of 8-hydroquinoline or its derivative arepentacene, tetracene, rubrene, tetrabenzoperylene, benzoperylene,coronene, perylene, benzotetracene, dibenzoanthracene, and quinacridone,and the compounds given in the aforegoing description of hole-injectinglayer. Particularly preferred are aromatic tertiary amine compounds andstyryl amine compounds.

The thickness of the above-mentioned layer should be smaller than thatof the light emitting layer, and is preferably 1 to 50 nm, particularlypreferably 5 to 30 nm. Such limitation of film thickness (controllingthe light emission region) is for the purpose of keeping the color ofemission light blue.

Moreover, it is still preferable that in the ratio of molecular numberin the adhesive layer, the ratio of metal complexes of8-hydroxyquinoline or its derivative is the largest. More preferably,the ratio in molecule number of the metal complexes of8-hydroxyquinoline or its derivative is 50% or more.

Similarly, preferred is a structure wherein the ratio of molecule numberis adjusted so as to the voltage required to emit the initial luminanceafter 100 hours of continuous light emission of the resulting device is1.1 times the initial voltage.

The adhesive layer is formed by, for instance, the spin-coating method,the casting method, or the deposition method. Preferably, the depositionmethod is used as in the forming of the light emitting layer and thehole injecting layer as described before.

According to the organic EL device of the present invention, it isrealized that the uniformity in light emitting face is improved, and thelowering in the initial luminance can be prevented. Accordingly, theminute processing, the improvement in productivity, and further thelonger lifetime of the device has come to be obtained.

Consequently, the organic EL device of the present invention is expectedto be effectively used as various light-emitting materials.

The present invention will be described in greater detail with referenceto the reference examples, the examples and the comparative examples asfollows.

REFERENCE EXAMPLE 1

[Preparation of 4,4'-bis(2,2-diphenylvinyl)biphenyl]

(1) Production of Arylene Group-Containing Phosphonate

9.0 g of 4,4'-bis(bromomethyl)biphenyl and 11 g of triethyl phosphitewere stirred on oil bath in a stream of argon for 6 hours while heatedat 140° C. Then, the excessive triethyl phosphite and by-produced ethylbromide were vacuum distilled away. The residue was allowed to standovernight to obtain 9.5 g of a white crystal (yield: 80%). The resultsof analyzing the product are as follows.

Melting point: 97.0° to 100.0° C.

Determination by proton nuclear magnetic resonance (¹ H-NMRCDCl₃): δ=7.0to 7.6 ppm (m; 8H, biphenylene ring-H) δ=3.1 ppm (d; 4H, J=20 Hz (³¹ P-¹H coupling) P-CH₂) δ=4.0 ppm (q; 8H, ethoxymethylene-CH₂) δ=1.3 ppm (t;12H, ethoxymethyl-CH₃)

The results as above were confirmed that the above-mentioned product wasan arylene group-containing phosphonate (phosphonate: Mw=454.5)represented by the formula: ##STR6## (2) Preparation of AromaticDimethylidine Compound

4.5 g of phosphonate as obtained in Reference Example 1 (1) and 5.5 g ofbenzophenone were dissolved into 100 ml of dimethylsulfoxide, and 2.2 gof potassium-t-butoxide was added thereto, and the mixture was stirredfor 4 hours in an argon stream at room temperature, then allowed tostand overnight.

To the resulting mixture, 100 ml of methanol was added, and the crystalprecipitated was filtered. The remainder was sufficiently washed threetimes with 100 ml of water, then three times with 100 ml of methanol,and purified on column to obtain 2.0 g of a yellowish orange powder(yield: 26%).

Analytical data of the product ape as follows.

Melting point: 204.5° to 206.5° C.

Determination by ¹ H-NMR (CDCl₃): δ=6.7 to 7.3 ppm (m; 30H, terminalphenyl ring-H, central biphenylene and methylidine ═C═CH--)

The result of an elementary analysis providing the composition formulaas C₄₀ H₃₀ was as follows. The values in the parentheses aretheoretical.

C: 94.23% (94.08%)

H: 5.84% (5.92%)

N: 0.00% (0%)

The infrared ray (IR) absorption spectrum (by KBr pellet method) is asfollows.

    ν.sub.C═C 1520, 1620 cm.sup.-1

By Mass Spectrum analysis, the molecular ion peak of the objectiveproduct, that is, m/Z=510 was detected out.

Above confirmed that the powder as the above-mentioned product was4,4'-bis(2,2-diphenylvinyl)biphenyl represented by the formula: ##STR7##

Examples 1 to 11

Indium tin oxide (ITO) was provided on a 25 mm×75 mm×1.1 mm glasssubstrate in a 100 nm thick film formed by the vapor deposition methodto obtain a transparent supporting substrate. Said substrate wasultrasonically washed with isopropylalcohol for 5 minutes and furtherfive minutes in pure water, then subjected to UV ozone washing for 10minutes in an apparatus manufactured by Samco International InstituteInc. Said transparent supporting substrate was attached to a substrateholder of a commercially available vapor deposition system (manufacturedby ULVAC Co., Ltd.), 200 mg ofN,N'-bis(3-methylphenyl)-N,N'-diphenyl[1,1'-biphenyl]-4,4'-diamine(TPD)was placed in an electrically-heated boat made of molybdenum, and 200 mgof 4,4'-bis(2,2-diphenylvinyl)biphenyl (DPVBi) obtained in ReferenceExample 1 was placed in another boat made of molybdenum, and thepressure in the vacuum chamber was decreased to 1×10⁻⁴ Pa. After that,said boat containing TPD was heated to 215° to 220° C., and TPD wasvapor-deposited on the transparent supporting substrate at a depositionrate of 0.1 to 0.3 nm/sec to obtain a hole injection layer of 60 nm infilm thickness. In this deposition process, the substrate was at roomtemperature.

Without taking the substrate out of the vacuum chamber, DPVBi fromanother boat was laminate-deposited in thickness of 40 nm on the holeinjection layer to form the light emitting layer. The deposition wasperformed with a boat temperature of 240° C. at a deposition rate of 0.1to 0.3 nm/sec, and the substrate was at room temperature.

Subsequently, the pressure in the vacuum chamber was raised to theatmospheric pressure, and 200 g of metal complexes of 8-hydroxyquinolineor its derivative as the material of the adhesive layer ((A) in Table 1)was newly placed in an electrically-heated boat made of molybdenum, andfurther 50 mg of an organic compound ((B) in Table 1) was added thereto,then the pressure of vacuum chamber was reduced to 1×10⁻⁴ Pa. Then, theboat containing (A) was heated ((C) in Table 1) with a deposition rateof 1.2 to 1.5 nm/sec, and the boat containing (B) was heated ((D) inTable 1) with a deposition rate of 0.01 to 0.03 nm/sec, thus they weredeposited simultaneously to form an adhesive layer with a film thicknessof 20 nm.

Then, the pressure of the vacuum chamber was raised to the atmosphericpressure, and a stainless steel mask was placed on said layer film,which was fixed on the substrate holder. In the electrically-heated boatmade of molybdenum, 1 g of magnesium ribbon was placed, and 500 mg ofsilver wire was placed in a tungsten basket, and the pressure wasreduced. After the pressure in the vacuum chamber was reduced to 1×10⁻⁴Pa, silver was deposited at the deposition rate of 0.1 nm/sec, andsimultaneously magnesium was deposited at a deposition rate of 1.4nm/sec to form a counter electrode with a film thickness of 150 nm.

Examples 12

A device was produced in the same manner as in Example except that1,1,4,4,-tetraphenyl-1,3-butadiene (energy gap: 2.80 eV) was used inplace of DPVBi.

Herein, energy gaps of (A) in Examples are shown as follows.

    ______________________________________                                        (A)                energy gap                                                 ______________________________________                                        tris(8-quinolinol)aluminum                                                                       2.50 eV                                                    bis(8-quinolinol)aluminum                                                                        2.43 eV                                                    tris(8-quinolinol)indium                                                                         2.33 eV                                                    bis(8-quinolinol)zinc                                                                            2.30 eV                                                    bis(8-quinolinol)zinc                                                                            2.20 eV                                                    ______________________________________                                    

                  TABLE 1                                                         ______________________________________                                                                       (C)    (D)                                     (A)                  (B)       °C.                                                                           °C.                              ______________________________________                                        Example 1                                                                             tris(8-quinolinol)aluminum                                                                     rubrene*.sup.1                                                                          230  310                                   Example 2                                                                             tris(8-quinolinol)aluminum                                                                     TPD*.sup.2                                                                              230  215                                   Example 3                                                                             tris(8-quinolinol)aluminum                                                                     Fastogen  230  350                                                            Super Red                                                                     7094Y*.sup.3                                         Example 4                                                                             bis(8-quinolinol)magnesium                                                                     rubrene*.sup.1                                                                          410  310                                   Example 5                                                                             bis(8-quinolinol)magnesium                                                                     TPD*.sup.2                                                                              410  215                                   Example 6                                                                             tris(8-quinolinol)indium                                                                       rubrene*.sup.1                                                                          315  310                                   Example 7                                                                             tris(8-quinolinol)indium                                                                       TPD*.sup.2                                                                              315  215                                   Example 8                                                                             bis(8-quinolinol)zinc                                                                          rubrene*.sup.1                                                                          315  310                                   Example 9                                                                             bis(8-quinolinol)zinc                                                                          TPD*.sup.2                                                                              315  215                                   Example 10                                                                            bis(8-quinolinol)zinc                                                                          Fastogen  315  350                                                            Super Red                                                                     7094Y*.sup.3                                         Example 11                                                                            bis(8-quinolinol)tin                                                                           TPD*.sup.2                                                                              220  215                                   Example 12                                                                            tris(8-quinolinol)aluminum                                                                     rubrene*.sup.1                                                                          230  310                                   ______________________________________                                         *.sup.1 produced by Aldrich Chemical Company, Inc.                            The structural formula is as follows.                                         ##STR8##                                                                      *.sup.2 N,N'-bis(3methylphenyl)-N,N'-diphenyl[1,1'-biphenyl]-4,4'-diamine     *.sup.3 produced by Dainippon Ink. & Chemical Incorp.                         The structural formula is as follows.                                         ##STR9##                                                                 

Comparative Example 1

On a 25 mm×75 mm×1.1 mm glass substrate, ITO was provided in a 100 nmthick film formed by the vapor deposition method to obtain a transparentsupporting substrate. Said substrate was ultrasonically washed withisopropyl alcohol for 5 minutes and further five minutes in pure water,then subjected to UV ozone washing for 10 minutes in an apparatusmanufactured by Samco International Institute Inc. Said transparentsupporting substrate was attached to a substrate holder of acommercially available vapor deposition system (manufactured by ULVACCo., Ltd.), 200 mg of TPD was placed in an electrically-heated boat madeof molybdenum, and 200 mg of DPVBi obtained in Reference Example 1 wasplaced in another boat made of molybdenum, and the pressure in thevacuum chamber was decreased to 1×10⁻⁴ Pa. After that, said boatcontaining TPD was heated to 215° to 220° C., and TPD wasvapor-deposited on the transparent supporting substrate at a depositionrate of 0.1 to 0.3 nm/sec to obtain a hole injecting layer of 60 nm infilm thickness. In this deposition process, the substrate was at roomtemperature. Without taking the substrate out of the vacuum chamber,DPVBi from another boat was laminate-deposited in thickness of 40 nm onthe hole injection layer to form the light emitting layer. Thedeposition was performed with a boat temperature of 240° C. at adeposition rate of 0.1 to 0.3 nm/sec, and the substrate was at roomtemperature.

The substrate was taken out from the vacuum chamber, a stainless steelmask was placed on said light emitting layer, which was fixed again onthe substrate holder. Subsequently, in a boat made of molybdenum, 200 mgof tris(8-quinolinol)aluminum (Alq₃) was placed and deposited in thevacuum chamber. Further, in the electrically-heated boat made ofmolybdenum, 1 g of magnesium ribbon was placed, and 500 mg of silverwire was placed in a tungsten basket, and deposited. After the pressurein the vacuum chamber was reduced to 1×10⁻⁴ Pa, the boat containing Alq₃was heated to 230° C., and deposited in a thickness of 20 nm at adeposition rate of 0.01 to 0.03 nm/sec. Further, silver was deposited atthe deposition rate of 0.1 nm/sec, and simultaneously, by theelectrically heating method, magnesium was deposited at a depositionrate of 1.4 nm/sec from another molybdenum boat to form a counterelectrode with a film thickness of 150 nm.

Comparative Example 2

On a 25 mm×75 mm×1.1 mm glass substrate, ITO was provided in a 100 nmthick film formed by the vapor deposition method to obtain a transparentsupporting substrate. Said substrate was ultrasonically washed withisopropyl alcohol for 5 minutes and further 5 minutes in pure water,then subjected to UV ozone washing for 10 minutes in an apparatusmanufactured by Samco International Institute Inc. Said transparentsupporting substrate was attached to a substrate holder of acommercially available vapor deposition system (manufactured by ULVACCo., Ltd.), 200 mg of TPD was placed in an electrically-heated boat madeof molybdenum, and 200 mg of DPVBi obtained in Reference Example 1 wasplaced in another boat made of molybdenum, and the pressure in thevacuum chamber was decreased to 1×10⁻⁴ Pa. After that, said boatcontaining TPD was heated to 215° to 220° C., and TPD wasvapor-deposited on the transparent supporting substrate at a depositionrate of 0.1 to 0.3 nm/sec to obtain a hole injecting layer of 60 nm infilm thickness. In this deposition process, the substrate was at roomtemperature. Without taking the substrate out of the vacuum chamber,DPVBi from another boat was laminate-deposited in thickness of 40 nm onthe hole injection layer to form the emitting layer. The deposition wasperformed with a boat temperature of 240° C. at a deposition rate of 0.1to 0.3 nm/sec, and the substrate was at room temperature.

The substrate was taken out from the vacuum chamber, a stainless steelmask was placed on said emitting layer, which was fixed again on thesubstrate holder. Subsequently, in a boat made of molybdenum, 200 mg ofbis(8-quinolinol)magnesium (Mgq₂) was placed and deposited on the vacuumchamber. Further, in the electrically-heated boat made of molybdenum, 1g of magnesium ribbon was placed, and 500 mg of silver wire was placedin a tungsten basket, and deposited. After the pressure in the vacuumchamber was reduced to 1×10⁻⁴ Pa, the boat containing Mgq₃ was heated to410° C., and deposited in a thickness of 20 nm at a deposition rate of0.01 to 0.03 nm/sec. Further, silver was deposited at the depositionrate of 0.1 nm/sec, and simultaneously, by the electrically heatingmethod, magnesium was deposited at a deposition rate of 1.4 nm/sec fromanother molybdenum boat to form a counter electrode with a filmthickness of 150 nm.

Comparative Example 3

On a 25 mm×75 mm×1.1 mm glass substrate, ITO was provided in a 100 nmthick film formed by the vapor deposition method to obtain a transparentsupporting substrate. Said substrate was ultrasonically washed withisopropyl alcohol for 5 minutes and further five minutes in pure water,then subjected to UV ozone washing for 10 minutes in an apparatusmanufactured by Samco International Institute Inc. Said transparentsupporting substrate was attached to a substrate holder of acommercially available vapor deposition system (manufactured by ULVACCo., Ltd.), 200 mg of TPD was placed in an electrically-heated boat madeof molybdenum, and 200 mg of DPVBi obtained in Reference Example 1 wasplaced in another boat made of molybdenum, and the pressure in thevacuum chamber was decreased to 1×10⁻⁴ Pa. After that, said boatcontaining TPD was heated to 215° to 220° C., and TPD wasvapor-deposited on the transparent supporting substrate at a depositionrate of 0.1 to 0.3 nm/sec to obtain a hole injection layer of 60 nm infilm thickness. In this deposition process, the substrate was at roomtemperature. Without taking the substrate out of the vacuum chamber,DPVBi from another boat was laminate-deposited in thickness of 40 nm onthe hole injecting layer to form the light emitting layer. Thedeposition was performed with a boat temperature of 240° C. at adeposition rate of 0.1 to 0.3 nm/sec, and the substrate was at roomtemperature.

The substrate was taken out from the vacuum chamber, a stainless steelmask was placed on said light emitting layer, which was fixed again onthe substrate holder. Subsequently, in a boat made of molybdenum, 200 mgof tris(8-quinolinol)indium (Inq₃) was placed and deposited on thevacuum chamber. Further, in the electrically-heated boat made ofmolybdenum, 1 g of magnesium ribbon was placed, and 500 mg of silverwire was placed in a tungsten basket, and deposited. After the pressurein the vacuum chamber was reduced to 1×10⁻⁴ Pa, the boat containing Inq₃was heated to 315° C., and deposited in a thickness of 20 nm at adeposition rate of 0.01 to 0.03 nm/sec. Further, silver was deposited atthe deposition rate of 0.1 nm/sec, and simultaneously, by theelectrically heating method, magnesium was deposited at a depositionrate of 1.4 nm/sec from another molybdenum boat to form a counterelectrode with a film thickness of 150 nm.

The devices obtained in Examples 1 to 12 and Comparative Examples 1 to 3were subjected to aging by applying DC electric field every two secondswith an interval of 4.2×10⁴ V/cm up to 1 to 1.3×10⁶ V/cm with ITO as theanode and metal electrodes as the cathodes in the atmosphere. Further,in Fluorinert® (FC-70, produced by Sumitomo 3M Ltd.), aging wasconducted for 10 minutes with an initial luminance of 100 cd/m².

The devices thus obtained were made to emit light continuously bydriving by DC in Fluorinert® with setting an initial luminance of 100cd/m². After 50 hours of the continuous light emitting, the devices wereevaluated on brightness and its uniformity under the conditions below.The results are shown in Table 2.

Uniformity: The devices were made to emit light at a brightness of 100cd/m², the emitting surfaces were observed by the use of a luminancemeter (CS-100, manufactured by Minolta Camera Co.), and evaluation wasmade as follows.

X: The region observed has non-emission region with a diameter of 10 μmor more, or has ununiformity in color.

∘: The region observed is uniformly emitted (without non-emission regionor ununiformity in color)

Further, after 100 hours of continuous light emitting, the luminance andthe voltage of the device were measured to find the ratio to the initialvoltage (the voltage after 100 hours/the initial voltage). The result isshown in Table 2.

                  TABLE 2                                                         ______________________________________                                                After 50 hours                                                                              After 100 hours                                                 of driving    of driving                                                      Luminance         Luminance Voltage                                           (cd/m.sup.2)                                                                          Uniformity                                                                              (cd/m.sup.2)                                                                            ratio                                     ______________________________________                                        Example 1 100       ◯                                                                           95      1.03                                    Example 2 100       ◯                                                                           93      1.03                                    Example 3 98        ◯                                                                           92      1.01                                    Example 4 100       ◯                                                                           94      1.05                                    Example 5 100       ◯                                                                           93      1.06                                    Example 6 95        ◯                                                                           91      1.05                                    Example 7 95        ◯                                                                           90      1.07                                    Example 8 98        ◯                                                                           92      1.03                                    Example 9 98        ◯                                                                           92      1.03                                    Example 10                                                                              95        ◯                                                                           90      1.05                                    Example 11                                                                              92        ◯                                                                           90      1.06                                    Example 12                                                                              92        ◯                                                                           90      1.09                                    Comparative                                                                             75        x         69      1.23                                    Example 1                                                                     Comparative                                                                             70        x         67      1.30                                    Example 2                                                                     Comparative                                                                             65        x         60      1.28                                    Example 3                                                                     ______________________________________                                    

What is claimed is:
 1. An organic electroluminescence device whichcomprises laminating layers in the order of anode/light emittinglayer/adhesive layer/cathode, or anode/hole-injecting layer/lightemitting layer/adhesive layer/cathode, wherein the adhesive layercomprises a metal complex of 8-hydroxyquinoline or a metal complex of a8-hydroxyquinoline derivative, said adhesive layer further comprising atleast one additional organic compound in an arbitrary region in thedirection of the thickness of the adhesive layer, the thickness of whichis smaller than that of the light emitting layer, and wherein the lightemitting layer has an energy gap larger than that of the metal complexof 8-hydroxyquinoline or the metal complex of 8-hydroxyquinolinederivative contained in the adhesive layer, and wherein the lightemitting layer comprises a compound which emits blue, greenish blue orbluish green light in CIE chromaticity coordinates.
 2. The organicelectroluminescence device as defined in claim 1 wherein the lightemitting layer comprises a compound represented by the general formula(I): ##STR10## wherein R¹ to R⁴ indicate each a hydrogen atom, an alkylgroup having 1 to 6 carbon atoms, an aralkyl group having 7 to 8 carbonatoms, an aryl group having 6 to 18 carbon atoms, a cyclohexyl group, anaryloxy group having 6 to 18 carbon atoms, or an alkoxy group having 1to 6 carbon atoms; wherein said aryl, cyclohexyl or aryloxy groups,independently may be substituted by one or more substituents selectedfrom the group consisting of an alkyl group having 1 to 6 carbon atoms,an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to8 carbon atoms, an aryloxy group having 6 to 18 carbon atoms, an acylgroup having 1 to 6 carbon atoms, an acyloxy group having 1 to 6 carbonatoms, a carboxyl group, a styryl group, an arylcarbonyl group having 6to 20 carbon atoms, an aryloxycarbonyl group having 6 to 20 carbonatoms, an alkoxycarbonyl group having 1 to 6 carbon atoms, ananilinocarbonyl group, a carbamoyl group, a phenyl group, a nitro group,a hydroxy group and a halogen; wherein R¹ to R⁴ may be the same ordifferent, and R¹ and R² or R³ and R⁴, may, independently, combine toform a substituted or unsubstituted saturated five-membered ring or asubstituted or unsubstituted saturated six-membered ring; Ar indicates asubstituted or unsubstituted arylene group having 6 to 20 carbon atoms,a single bond, or a conjugated polyene having 2 to 6 carbon atoms;wherein said arylene group may be mono-substituted or poly-substituted,and may be any of ortho-, para- and meta-arylene; however, when Ar is anunsubstituted phenylene, R¹ to R⁴ are each selected from the groupconsisting of an alkoxy group having 1 to 6 carbon atoms, an aralkylgroup having 7 to 8 carbon atoms, a substituted or unsubstitutednaphthyl group, a biphenyl group, a cyclohexyl group, and an aryloxygroup,or general formula (II):

    A--Q--B                                                    (II)

wherein A and B indicate each a monovalent group which is obtained byremoving a hydrogen atom from the compound represented by the abovegeneral formula (I), and may be identical to or different from eachother; Q indicates a divalent group breaking the conjugation system, orgeneral formula (III) ##STR11## wherein A¹ indicates a substituted orunsubstituted arylene group having 6 to 20 carbon atoms or a divalentaromatic heterocyclic group; A¹ has a position of bond site which may beany of ortho-, meta and para-; A² is a substituted or unsubstituted arylgroup having 6 to 20 carbon atoms or a monovalent aromatic heterocyclicgroup; R⁵ and R⁶ indicate each a hydrogen atom, a substituted orunsubstituted aryl group having 6 to 20 carbon atoms, a cyclohexylgroup, a monovalent aromatic heterocyclic group, an alkyl group having 1to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or analkoxy group having 1 to 10 carbon atoms; R⁵ and R⁶ may be the same ordifferent and may be mono-substituted by an alkyl group, an aryloxygroup, an amino group, or a phenyl group with or without a substituent;wherein each substituent of R⁵ may combine with A¹ to form a saturatedor unsaturated five-membered ring or six-membered ring, and similarlyeach substituent of R₆ may combine with A² to form a saturated orunsaturated five-membered ring or six-membered ring; and Q indicates adivalent group breaking the conjugation.
 3. The organicelectroluminescence device as defined in claim 2 wherein the adhesivelayer is a mixture of a metal complex of 8-hydroxyquinoline or a metalcomplex of a 8-hydroxyquinoline derivative and at least one additionalorganic compound, and the metal complex of 8-hydroxyquinoline or metalcomplex of 8-hydroxyquinoline derivative is the most abundant componenton a molar basis in the adhesive layer.
 4. The organicelectroluminescence device as defined in claim 2 wherein the adhesivelayer is a mixture of a metal complex of 8-hydroxyquinoline or a metalcomplex of a 8-hydroxyquinoline derivative and at least one additionalorganic compound, and wherein the total amount of the at least oneadditional organic compound in the adhesive layer is at least 0.01 mol%, and the amount of the metal complex of 8-hydroxyquinoline or themetal complex of the 8-hydroxyquinoline derivative in the adhesive layeris 50 mol % or more.
 5. The organic electroluminescence device asdefined in claim 2 wherein the metal complex of a 8-hydroxyquinolinederivative is a chelated oxinoide compound.
 6. The organicelectroluminescence device as defined in claim 5 wherein the chelatedoxinoide compound is tris(8-quinolinol)aluminum,bis(8-quinolinol)magnesium, bis(benzo-8-quinolinol)zinc,bis(2-methyl-8-quinolato)aluminumoxide, tris(8-quinolinol)indium,tris(5-methyl-8-qinolinol)aluminum, 8-quinolinol lithium,tris(5-chloro-8-quinolinol)gallium, bis(5-chloro-8-quinolinol)calcium,5,7-dichloro-8-qinolinolaluminum,tris(5,7-dibromo-8-hydroxyquinolinol)aluminum,bis(8-quinolinol)beryllium, bis(2-methyl-8-quinolinol)beryllium,bis(8-quinolinol)zinc, bis(2-methyl-8-quinolinol)zinc,bis(8-quinolinol)tin, or tris(7-propyl-8-quinolinol)aluminum.
 7. Theorganic electroluminescence device according to claim 2, wherein Ar isan ortho, para or meta arylene group which may be monosubstituted orpolysubstituted.